The biggest argument game developers have come up so far is “Linux marketshare is what prevents us from developing games for Linux blah blah blah…”. At this point, in order to avoid such claims, Linux gamers should show that they are live and kicking. Send mails, e-mails to the game developers; write about the lack of support on your blog, microblogs; talk to your friends about it and so on, so forth. To put it another way: “Raise awareness!”
Actually there’s a better way to enhance this awareness: Buy Linux games (Penumbra series is should be a very good start, for instance). This way other developers would see that there’s potential for investing in Linux.